Providing Wavelength Connectivity Information To A Network

ABSTRACT

In particular embodiments, providing wavelength connectivity information to a network includes establishing wavelength connectivity information for a network node of the network. The network node comprises link pairs, where a link pair has an input link and an output link. The wavelength connectivity information describes a set of available wavelengths between an input link and an output link. The wavelength connectivity information is inserted into an advertisement, and the advertisement is sent to at least a subset of the network nodes of the network in real time.

TECHNICAL FIELD

This invention relates generally to the field of communication networksand more specifically to providing wavelength connectivity informationto a network.

BACKGROUND

A network includes network nodes through which circuits, or paths, maybe set up. Setting up circuits typically involves information aboutabilities and constraints of the network nodes. Known techniques fordetermining this information, however, may not be effective in certainsituations.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 illustrates an embodiment of a network that includes networknodes;

FIG. 2 illustrates one embodiment of a portion of the network of FIG. 1for which signal reachability information may be advertised;

FIGS. 3A through 4B illustrate examples of wavelength connectivityinformation that may be advertised; and

FIG. 5 illustrates one embodiment of a method for setting up a circuit.

DETAILED DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention and its advantages are bestunderstood by referring to FIGS. 1 through 5 of the drawings, likenumerals being used for like and corresponding parts of the variousdrawings.

Overview

In particular embodiments, providing wavelength connectivity informationto a network includes establishing wavelength connectivity informationfor a network node of the network. The network node comprises linkpairs, where a link pair has an input link and an output link. Thewavelength connectivity information describes a set of availablewavelengths between an input link and an output link. The wavelengthconnectivity information is inserted into an advertisement, and theadvertisement is sent to at least a subset of the network nodes of thenetwork in real time.

Description of Examples

FIG. 1 illustrates an embodiment of a network 10 that includes networknodes 22. In particular embodiments, a link (for example, a trafficengineering (TE) link) of network node 22 may be configured to establishwavelength connectivity information that describes a set of availablewavelengths between links (for example, traffic engineering (TE) links)of network node 22. Network node 22 may insert the signal reachabilityinformation in an advertisement (such as a traffic engineering linkadvertisement) and send the advertisement to other network nodes 22. Theinformation may be provided in real time.

In the illustrated embodiment, network 10 represents a communicationnetwork that allows components, such as nodes, to communicate with othercomponents. A communication network may comprise all or a portion of oneor more of the following: a public switched telephone network (PSTN), apublic or private data network, a local area network (LAN), ametropolitan area network (MAN), a wide area network (WAN), a local,regional, or global communication or computer network such as theInternet, a wireline or wireless network, an enterprise intranet, othersuitable communication link, or any combination of any of the preceding.

According to the illustrated embodiment, network 10 includes a ringnetwork 20. Ring network 20 includes network nodes 22 and spans 26. Inone embodiment, ring network 20 communicates information throughsignals. A signal may comprise an optical signal transmitted as lightpulses. As an example, an optical signal may have a frequency ofapproximately 1550 nanometers and a data rate of 10, 20, 40, or over 40gigabits per second (G). A signal may comprise a synchronous transportsignal (STS) that communicates information in packets. Information mayinclude voice, data, audio, video, multimedia, control, signaling,and/or other information. A signal may travel through a circuit, orpath, from a source network node 22 to a destination network node 22.

According to one embodiment, ring network 20 may utilize protocols suchas Resilient Packet Ring (RPR) protocols, according to which packets areadded, passed through, or dropped at each network node 22. Ring network20 may utilize any suitable routing technique, such as GeneralizedMulti-Protocol Label Switching (GMPLS) techniques. Ring network 20 mayutilize any suitable transmission technique, such as wavelength divisionmultiplexing (WDM) techniques.

In the illustrated embodiment, network nodes 22 include any suitabledevices such as network elements operable to route packets through, to,or from ring network 20. Examples of network elements include routers,switches, wavelength division multiplexers (WDMs), access gateways,endpoints, softswitch servers, trunk gateways, access service providers,Internet service providers, or other device operable to route packetsthrough, to, or from ring network 20.

A network node 22 may include logic, such as control plane logic and/orbearer plane logic. Control plane logic manages routing of packets, andbearer plane logic routes the packets.

A network node 22 includes links 30 (30 a and/or 30 b) that processincoming and/or outgoing signals. In particular embodiments, links 30represent traffic engineering (TE) links. A traffic engineering link maybe a subinterface capable of carrying Generalized Multi Protocol LabelSwitching (GMPLS) traffic engineered traffic. A link 30 may be an inputlink 30 a that receives an input signal for node 22 or an output link 30b that sends an output signal from node 22. A link pair comprises aninput link 30 a and output link 30 b of a path that communicates asignal.

Spans 26 represent any suitable fibers operable to transmit a signal,such as optical fibers. A span 26 communicates one or more channels,where a channel represents a particular wavelength. A wavelength may beidentified by a wavelength channel identifier.

In particular embodiments, a link 30 (such as a traffic engineeringlink) of network node 22 may be configured to establish signalreachability information that describes attributes that affect thereachability of an optical signal. Link 30 may insert the signalreachability information in an advertisement (such as a trafficengineering link advertisement) and send the advertisement to othernetwork nodes 22. Network node 22 may use the GMPLS protocol todistribute signal reachability information while on-line or off-line.

In particular embodiments, a link 30 (for example, a traffic engineeringlink) of network node 22 may be configured to establish wavelengthconnectivity information that describes wavelength availability betweenan input link 30 a and output link 30 b. Network node 22 may insert thesignal reachability information in an advertisement (such as a trafficengineering link advertisement) and send the advertisement to othernetwork nodes 22. The information may be provided in real time.

In particular embodiments, control plane logic of network node 22 may beconfigured to establish that planning pre-conditions for planning acircuit have been satisfied and to initiate the planning of the circuit.The control plane logic may also establish that reservationpre-conditions for reservation of resources for the circuit have beensatisfied and initiate reservation of the resources for the circuit. Thecontrol plane logic may also establish that activation pre-conditionsfor activation of the circuit have been satisfied and initiate theactivation of the circuit.

A component of system 10 may include an interface, logic, memory, and/orother suitable element. An interface receives input, sends output,processes the input and/or output, and/or performs other suitableoperation. An interface may comprise hardware and/or software.

Logic performs the operations of the component, for example, executesinstructions to generate output from input. Logic may include hardware,software, and/or other logic. Logic may be encoded in one or moretangible media and may perform operations when executed by a computer.Certain logic, such as a processor, may manage the operation of acomponent. Examples of a processor include one or more computers, one ormore microprocessors, one or more applications, and/or other logic.

A memory stores information. A memory may comprise one or more tangible,computer-readable, and/or computer-executable storage medium. Examplesof memory include computer memory (for example, Random Access Memory(RAM) or Read Only Memory (ROM)), mass storage media (for example, ahard disk), removable storage media (for example, a Compact Disk (CD) ora Digital Video Disk (DVD)), database and/or network storage (forexample, a server), and/or other computer-readable medium.

Modifications, additions, or omissions may be made to network 10 withoutdeparting from the scope of the invention. The components of network 10may be integrated or separated. Moreover, the operations of network 10may be performed by more, fewer, or other components. Additionally,operations of network 10 may be performed using any suitable logic. Asused in this document, “each” refers to each member of a set or eachmember of a subset of a set.

FIG. 2 illustrates one embodiment of a portion of network 10 of FIG. 1for which signal reachability information may be advertised. Inparticular embodiments, a link 30 of network node 22 may be configuredto establish signal reachability information that describes attributesthat affect the reachability of an optical signal. Link 30 may insertthe signal reachability information in an advertisement and send theadvertisement to other network nodes 22. Network node 22 may use theGMPLS protocol to distribute signal reachability information whileon-line or off-line. Attributes may be distributed with incoming and/oroutgoing advertisements.

In particular embodiments, signal reachability information describesattributes that affect the reachability of an optical signal. Opticalsignals have limited reach. As a signal travels through a circuit, thesignal may be modified (such as attenuated or distorted) and fail tocommunicate the information that it carries. The reachability of asignal may describe the reach that the signal has before failing tocommunicate information.

An attribute may result from physical features of components of acircuit. Attributes include nodal attributes and span attributes. Anodal attribute of a network node 22 results from physical features thenetwork node 22 (such as the type of device). Examples of nodalattributes include a node optical signal-to-noise ratio (OSNR), a nodepolarization mode dispersion (PMD), a node cross-talk (XT), a nodepass-band narrowing (PBN), and a node dispersion.

Different paths within a network node 22 may have different physicalfeatures, so different paths may have different nodal attributes. In theillustrated embodiment, the portion includes physical components 44 (44a, 44 b, . . . , and/or 44 e) of network node 22. Components 44 mayaffect the signal reachability of a signal 40.

In the illustrated embodiment, paths 46 (46 a, 46 b, and/or 46 c)through network node 22 pass through components 44. A drop path 46 apasses through components 44 a and 44 d; a pass-thru path 46 b passesthrough components 44 a, 44 b, and 44 c; and an add path 46 c passesthrough components 44 c and 44 e. Components 44 of a path 46 affect thenodal attributes of path 46. For example, components 44 a and 44 daffect nodal attributes of drop path 46 a. A nodal attribute of a path46 may be associated with a starting link 30 and an ending link 30 ofthe path 46.

Span attributes result from physical features (such as fiber type) ofthe span. Examples of span attributes include an incoming spandispersion, an incoming span polarization mode dispersion (PMD), anincoming span cross-talk (XT), and an outgoing transmit optical power.Span attributes for a wavelength of a span 26 may be associated with awavelength channel identifier of the wavelength.

In particular embodiments, signals 40 from a first output link 30 btravel through a first span 26 to a first input link 30 a of networknode 22. As signals 40 travel through first span 26, span attributes offirst span 26 affect the signal reachability of signals 40. Signals 40may travel across a drop path 46 a, a pass-thru path 46 b, or an addpath 46 c of network node 22. Nodal attributes of the traveled path 46affect signal 40. From output link 30 b, signals 40 travel through asecond span 26 to a second input link 30 a. Span attributes of secondspan 26 affect the reachability of signals 40.

In particular embodiments, a link 30 sends advertisements that includesignal reachability information associated with link 30, for example,information about attributes that affect reachability of a signalentering and/or leaving link 30. For example, input link 30 a sendsadvertisements that include span attributes of first span 26 and/ornodal attributes of drop path 46 a. Examples of the span attributesinclude a span dispersion, polarization mode dispersion, and/orcross-talk. Examples of the nodal attributes include a node polarizationmode dispersion, optical signal-to-noise ratio, cross-talk, pass bandnarrowing, and/or dispersion.

In the example, output link 30 b sends advertisements that include nodalattributes of a pass-thru path 46 b and/or add path 46 c. Examples ofthe nodal attributes include a node polarization mode dispersion,optical signal-to-noise ratio, cross-talk, pass band narrowing,dispersion, and/or transmit power.

A nodal attribute advertisement for an attribute may include thestarting link 30 and ending link 30 of the path with the attribute, thesignal type, and the nodal attribute. For example, the advertisement forPMD may include the starting link, ending link, signal type, and PMD.Signal type may indicate the data rate of the signal, for example, 2.5G, 10 G, 40 G, or greater. The signal type may also indicate whetherthere is a forward error correction (FEC), out-of-band (OOB), or maximumlikelihood sequence estimate (MLSE).

A span attribute advertisement of a wavelength may include thewavelength channel identifier of the wavelength and the span attribute.For example, the advertisement for 2.5 g/10 g incoming span dispersionmay include the incoming span dispersion plus and incoming dispersionminus. The 40 g incoming span dispersion may include the wave channelidentifier, incoming span dispersion, incoming span average dispersion,incoming span dispersion deviation, incoming dispersion compensationmodule (DCM) average dispersion, and incoming DCM dispersion deviation.The 2.5 g/10 g span dispersion target may specify the acceptable totalspan dispersion target for a signal type.

In particular embodiments, a path engine 48 of network node 22calculates the path for a circuit. Path engine 48 may include acalculated shortest path first (CSPF), explicit route object (ERO), orother suitable path calculation engine.

In particular embodiments, path engine 48 gathers signal reachabilityinformation to calculate the signal reachability of a circuit. Signalreachability for a circuit may be calculated from the values for thenodal and/or span attributes of the circuit, as discussed below. Inparticular embodiments, path engine 48 may receive a signal request thatincludes, for example, a signal rate request, such as 2.5 G, 10 G, or 40G. Path engine 48 determines if the signal reachability of the circuitcan satisfy the request. If an attribute fails to satisfy an attributethreshold, then the circuit is not reachable. In certain embodiments, anattribute threshold depends on the signal type.

Path engine 48 may calculate the circuit attributes of circuit signalreachability in any suitable manner. In particular embodiments, acircuit attribute may be calculated from a function of the values of theattributes of the circuit. Certain attributes may have values for spanattributes, nodal attributes, or both span and nodal attributes. In oneexample, a circuit starts at a source network node 22, passes throughvarious spans 26 and intermediate network nodes 22, and ends atdestination network node 22. Criteria attributes may be calculated froma function of the values of the nodal attributes of an add path 46 a ofsource network node 22, span attributes of the spans 26, nodalattributes of the pass-thru paths 46 b of intermediate network nodes 22,and/or nodal attributes of a drop path 46 b of destination network node22.

Below are examples of functions that may be used to calculate circuitattributes from the values of the attributes of the circuit. In theexamples, ATTX represents a nodal or span attribute. If ATTX representsa nodal attribute for a path of a network node, then ATTX may beexpressed as ATT_(path,node). Add may represent an add path 46 a, Passmay represent a pass-thru path 46 b, and Drop may represent a drop path46 c. Source may represent a source network node, Int may represent anintermediate network node, and Dest may represent a destination networknode. Intermediate network node j, where j=1, . . . , M, may berepresented by Int_(j). If ATT_(X) represents a span attribute, thenATT_(X) may be expressed as ATT_(Spani), where Spani represents span iof a circuit, where i=1, . . . , N.

In particular embodiments, the polarization mode dispersion (PMD) of acircuit may be calculated according to the following function:

${{{Total}P}\; M\; D} = \sqrt{\begin{matrix}{{P\; M\; D_{{Add},{Source}}^{2}} + {\sum\limits_{i = 1}^{N}\; {P\; M\; D_{Spani}^{2}}} +} \\{{\sum\limits_{j = 1}^{M}\; {P\; M\; D_{{Pass},{Intj}}^{2}}} + {P\; M\; D_{{Drop},{Dest}}^{2}}}\end{matrix}}$

The circuit attribute need not include both span and nodal attributes.For example, the total OSNR may be calculated according to the followingequation:

${TotalOSNR} = {{{- 10} \times {\log_{10}\begin{pmatrix}{{OSNR}_{{Add},{Source}} +} \\{{\sum\limits_{j = 1}^{M}\; {OSNR}_{{Pass},{Intj}}} +} \\{OSNR}_{{Drop},{Dest}}\end{pmatrix}}} - {OSNR}_{penalty}}$

The OSNR_(penalty) may be computed according to:

${OSNR}_{penalty} = {\sum\limits_{2}^{P}\; {ATT\_ OSNR}_{penaltyk}}$

where ATT_OSNR_(penaltyk) represents an OSNR penalty of a particularattribute k, where k=1, 2, . . . , P.

An attribute OSNR penalty may be computed in any suitable manner. Forexample, a pass-band narrowing (PBN) OSNR penalty may be calculatedaccording to:

${PBN\_ OSNR}_{penalty} = {{P\; B\; N_{{Add},{Source}}} + {\sum\limits_{j = 1}^{M}\; {P\; M\; D_{{Pass},{Intj}}}} + \ldots + {P\; B\; N_{{drop},{dest}}}}$

A cross-talk OSNR penalty may be calculated according to:

XT _(—) OSNR _(penalty) =XTCoeff _(A)×exp(XTCoeff _(B)×TotalXT)

where TotalXT represents the total cross-talk and XTCoeff_(A) andXTCoeff_(B) represent cross-talk coefficients A and B, respectively. Thetotal cross-talk may be calculated according to:

${{Total}\mspace{14mu} {XT}} = {10 \times {\log_{10}\begin{bmatrix}{10^{{XTAdd},{{Source}/10}} + {\sum\limits_{i = 1}^{N}\; 10^{{XTSpani}/10}} +} \\{{\sum\limits_{j = 1}^{M}\; 10^{{XTPass},{{Intj}/10}}} + 10^{{XTDrop},{{Dest}/10}}}\end{bmatrix}}}$

Cross-talk coefficients A and B may depend on the signal rate of therequested signal.

A polarization mode dispersion (PMD) OSNR penalty may be calculatedaccording to:

PMD _(—) OSNR _(penalty) =PMDCoeff _(A) ×PMDtmp ³ +PMDCoeff _(B) ×PMDtmp² +PMDCoeff _(B) ×PMPtmp+PMDCoeff _(D)−0.5

where PMDtmp is calculated from the total PMD and bitrate, andPMDCoeff_(A) through PMDCoeff_(D) represent PMD Coefficients A throughD, respectively. The PMD coefficients and bitrate may depend onrequested signal rate. Other attributes OSNR penalties may becalculated, such as a dispersion and other penalties.

FIGS. 3A through 4B illustrate examples of wavelength connectivityinformation that may be advertised. In particular embodiments, a link 30of network node 22 may be configured to establish wavelengthconnectivity information that describes wavelength availability betweenan input link 30 a and output link 30 b. Link 30 may insert the signalreachability information in an advertisement and send the advertisementto other network nodes 22. The information may be provided in real timefor all the appropriate combinations between the input links 30 a andoutput links 30 b of network node 22.

In particular embodiments, wavelength connectivity information describeswavelength availability between an input link 30 a and an output link 30b of a link pair. Wavelength connectivity information may indicate oneor more wavelengths available between input link 30 a and output link 30b, whether the signal is regenerated, whether a wavelength is converted,and/or whether a wavelength can be added or dropped.

In particular embodiments, the advertised information may include theidentifier of input link 30a, one or more allowed incoming wavelengths,one or more allowed outgoing wavelengths, and/or signal type.Wavelengths may be designated by the channel identifier of thewavelength. The signal type may indicate whether the signal may undergooptical-to-electrical-to-optical (O-E-O) regeneration.

In particular embodiments, certain values may be set to zero. Forexample, an input link identifier may be set to zero if theadvertisement applies to all links of node 22. As another example, anallowed incoming wavelength may be set to zero if all appropriatewavelengths are allowed. As yet another example, an outgoing wavelengthmay be set to zero if there is no wavelength conversion. Zero valuesneed not be advertised, which may reduce the size of information to beadvertised.

FIG. 3A illustrates a situation in which any wavelength channel at inputlink 30 a is allowed to connect to any wavelength channel at output link30b. The advertisement may indicate that the allowed from linkidentifier is link A, the allowed from wavelength channel identifier is0, and the allowed to wavelength channel identifier is 0.

FIG. 3B illustrates a situation in which a first wavelength channel λ₁at input link 30 a is allowed to connect withoptical-to-electrical-to-optical conversion to the first wavelengthchannel λ₁ at output link 30 b. The advertisement may indicate that theallowed from link identifier is link A, the allowed from wavelengthchannel identifier is λ₁, and the allowed to wavelength channelidentifier is 0.

FIG. 3C illustrates a situation in which a first wavelength channel λ₁at input link 30 a is allowed to connect withoptical-to-electrical-to-optical conversion to a second wavelengthchannel λ₂ at output link 30 b. The advertisement may indicate that theallowed from link identifier is link A, the allowed from wavelengthchannel identifier is λ₁, and the allowed to wavelength channelidentifier is λ₂.

FIG. 4A illustrates a situation in which a first wavelength channel frominput link 30 a is allowed to drop to first wavelength channel λ₁ atoutput link 30 b. The advertisement may indicate that the allowed fromlink identifier is link A, the allowed from wavelength channelidentifier is λ₁, and the allowed to wavelength channel identifier is 0.

FIG. 4B illustrates a situation in which a first wavelength channel frominput link 30 a is allowed to add to the first wavelength channel at theoutput link 30 b. The advertisement may indicate that the allowed fromlink identifier is link A, the allowed from wavelength channelidentifier is λ₁, and the allowed to wavelength channel identifier is 0.

FIG. 5 illustrates one embodiment of a method for setting up a circuit.In particular embodiments, control plane logic may be configured toestablish that planning pre-conditions for planning a circuit have beensatisfied and initiate the planning of the circuit. The control planelogic may also establish that reservation pre-conditions for reservationof resources for the circuit have been satisfied and initiatereservation of the resources for the circuit. The control plane logicmay also establish that activation pre-conditions for activation of thecircuit have been satisfied and initiate the activation of the circuit.In particular embodiments, establishing that a pre-condition has beensatisfied may involve receiving a message that pre-condition has beensatisfied.

The method includes a planning stage 110, a reservation stage 114, andan activation stage 118. An optical network may be designed andinstalled at step 120. The control plane logic may establish that one ormore planning pre-conditions have been satisfied prior to initiatingplanning stage 110. Examples of planning pre-conditions may includenetwork nodes 22 have been configured and are running,wavelength-division multiplexing (WDM) facilities have been provisioned,and spans 26 have been installed. The control plane logic may initiateplanning stage 110 by sending a planning command that includes sourcenetwork node 22 and destination network node 22 of a circuit to bedesigned.

At planning stage 110, the circuit may be designed at step 124 ofplanning stage 110. Circuit design may involve determining of the nodes22 of the circuit and may take into account information provided byadvertisements sent from the network nodes 22. For example, the designmay take into account the wavelength connectivity information and thesignal reachability information. The path of the circuit may be storedin a database. Control plane logic may provide design validation at step128. Design validation validates the design of the circuit path.

The control plane logic may establish that one or more reservationpre-conditions have been satisfied prior to initiating reservation stage114. Examples of reservation pre-conditions may include the circuit hasbeen designed, the equipment has been provisioned, and the spans 26 andnodes 22 have been connected. The control plane logic may initiatereservation of the resources for the circuit by sending a reservationcommand.

At reservation stage 114, resources are provisioned at step 132.Resources are reserved by the control plane logic at step 136. Resourcesmay include optical and/or physical resources such as channel, route,cross-connect points, and optical line card shelf resources. The networkresources may be reserved from end to end by signaling.

The control plane logic may establish that one or more activationpre-conditions have been satisfied prior to initiating activation stage118. Examples of activation pre-conditions include resource reservationhas been completed and equipment has been installed. The control planelogic may initiate activation of the circuit by sending an activationcommand.

At activation stage 118, the circuit is installed at step 140. Equipmentand fiber connections may be installed based upon the reservation entry.The path may be validated by the control plane logic at step 144. Thecontrol plane logic may activate the path at step 148. Databasenotifications may be sent to indicate the change of state of the nodes22 of the path.

Modifications, additions, or omissions may be made to the methodswithout departing from the scope of the invention. The method mayinclude more, fewer, or other steps. Additionally, steps may beperformed in any suitable order.

Certain embodiments of the invention may provide one or more technicaladvantages. A technical advantage of one embodiment may be that a link(for example, a traffic engineering link) of a network node may beconfigured to establish wavelength connectivity information thatdescribes a set of available wavelengths between links (for example,traffic engineering links) of the network node. The network node mayadvertise the information to other network nodes in real time.

Certain embodiments of the invention may include none, some, or all ofthe above technical advantages. One or more other technical advantagesmay be readily apparent to one skilled in the art from the figures,descriptions, and claims included herein.

Although this disclosure has been described in terms of certainembodiments, alterations and permutations of the embodiments will beapparent to those skilled in the art. Accordingly, the above descriptionof the embodiments does not constrain this disclosure. Other changes,substitutions, and alterations are possible without departing from thespirit and scope of this disclosure, as defined by the following claims.

1. A method comprising: establishing wavelength connectivity informationfor a network node of a plurality of network nodes of a network, thenetwork node comprising a plurality of link pairs, a link paircomprising an input link and an output link, the wavelength connectivityinformation describing wavelength availability between the input linkand the output link of at least a subset of the link pairs; insertingthe wavelength connectivity information into an advertisement; andsending the advertisement to at least a subset of the network nodes ofthe network in real time.
 2. The method of claim 1, the wavelengthconnectivity information indicating a signal type.
 3. The method ofclaim 1, the wavelength connectivity information identifying: an inputwavelength channel at the input link; and an output wavelength channelat the output link.
 4. The method of claim 1, the wavelengthconnectivity information indicating: any wavelength channel at the inputlink is allowed to connect to the any wavelength channel at the outputlink.
 5. The method of claim 1, the wavelength connectivity informationindicating: a first wavelength channel at the input link is allowed toconnect to the first wavelength channel at the output link.
 6. Themethod of claim 1, the wavelength connectivity information indicating: afirst wavelength channel at the input link is allowed to connect to asecond wavelength channel at the output link.
 7. The method of claim 1,the wavelength connectivity information indicatingoptical-to-electrical-to-optical wavelength conversion.
 8. The method ofclaim 1, the wavelength connectivity information indicating: a firstwavelength channel from the input link is allowed to drop to the firstwavelength channel.
 9. The method of claim 1, the wavelengthconnectivity information indicating: a first wavelength channel to theoutput link is allowed to add to the first wavelength channel.
 10. Themethod of claim 1, the advertisement comprising a traffic engineering(TE) link advertisement.
 11. One or more computer-readable tangiblemedia encoding software operable when executed to: establish wavelengthconnectivity information for a network node of a plurality of networknodes of a network, the network node comprising a plurality of linkpairs, a link pair comprising an input link and an output link, thewavelength connectivity information describing wavelength availabilitybetween the input link and the output link of at least a subset of thelink pairs; insert the wavelength connectivity information into anadvertisement; and send the advertisement to at least a subset of thenetwork nodes of the network in real time.
 12. The computer-readabletangible media of claim 11, the wavelength connectivity informationindicating a signal type.
 13. The computer-readable tangible media ofclaim 11, the wavelength connectivity information identifying: an inputwavelength channel at the input link; and an output wavelength channelat the output link.
 14. The computer-readable tangible media of claim11, the wavelength connectivity information indicating: any wavelengthchannel at the input link is allowed to connect to the any wavelengthchannel at the output link.
 15. The computer-readable tangible media ofclaim 11, the wavelength connectivity information indicating: a firstwavelength channel at the input link is allowed to connect to the firstwavelength channel at the output link.
 16. The computer-readabletangible media of claim 11, the wavelength connectivity informationindicating: a first wavelength channel at the input link is allowed toconnect to a second wavelength channel at the output link.
 17. Thecomputer-readable tangible media of claim 11, the wavelengthconnectivity information indicating optical-to-electrical-to-opticalwavelength conversion.
 18. The computer-readable tangible media of claim11, the wavelength connectivity information indicating: a firstwavelength channel from the input link is allowed to drop to the firstwavelength channel.
 19. The computer-readable tangible media of claim11, the wavelength connectivity information indicating: a firstwavelength channel to the output link is allowed to add to the firstwavelength channel.
 20. The computer-readable tangible media of claim11, the advertisement comprising a traffic engineering (TE) linkadvertisement.
 21. A system comprising: means for establishingwavelength connectivity information for a network node of a plurality ofnetwork nodes of a network, the network node comprising a plurality oflink pairs, a link pair comprising an input link and an output link, thewavelength connectivity information describing wavelength availabilitybetween the input link and the output link of at least a subset of thelink pairs; means for inserting the wavelength connectivity informationinto an advertisement; and means for sending the advertisement to atleast a subset of the network nodes of the network in real time.